Polycarbonate vs. PETG: Material Differences and Comparisons

Polycarbonate (PC) is an amorphous thermoplastic known for its high optical clarity, with light transmission properties comparable to glass (typically around 88-92%). It is widely used as a glass substitute due to its superior impact resistance and durability. In addition to its optical qualities, PC is valued for its excellent resistance to impact, heat, and dimensional stability. Typical applications include automotive light lenses, optical lenses and eyewear, lighting enclosures, greenhouse glazing, medical components, and personal protective equipment (PPE).

PETG (Polyethylene Terephthalate Glycol-modified) is a copolyester thermoplastic engineered for enhanced clarity, toughness, and processability. It is used across various industries due to its high impact strength and resistance to a broad range of chemicals and solvents. PETG is especially prevalent in packaging applications, including food, beverage, and consumer product containers. A significant portion of PETG is used in the manufacture of liquid containers due to its food-safe properties, chemical stability, and resistance to pressure-related deformation, such as creep caused by carbonation in sealed bottles.

This article will compare Polycarbonate and PETG in terms of their mechanical properties, optical and thermal performance, chemical resistance, application suitability, and cost-efficiency.

What Is Polycarbonate?

Polycarbonate (PC) is an amorphous thermoplastic. It is generally considered interchangeable with polymethylmethacrylate (PMMA, or acrylic), although PMMA has a lower refractive index (1.48), making it less effective for some optical applications. Molded PC has higher light transmissivity than glass and is widely used as a substitute for glass. Polycarbonate is widely used due to its durability and impact strength. Its scratch resistance is poor, but hard coats counter this. It is suitable for eyewear and lenses because of its relatively high refractive index of 1.58 (allowing thinner lenses for the same focal effect). Low molecular weight grades of PC offer poorer properties than higher molecular weight grades, but easier processing. Choosing between cost and toughness drives selection; for example, the higher weight grades are widely employed in the aerospace industry.

The toughness of PC is valuable, and it is widely used in automotive applications. The UV stability of PC is relatively low, but adding coatings and antioxidants increases its lifespan. So vehicle light covers don’t yellow and embrittle, as they used to. PC is useful for roofing applications because it is rigid, relatively low-cost, highly transparent in the visible spectrum, and virtually opaque to UV. PC is also a critical copolymer addition, enhancing strength and rigidity to other polymers. However, PC is highly vulnerable to attacks by oils, solvents, and organic acids, which rapidly break down and destroy the polymer. This property carries over into many of PC’s copolymer uses.

What Is PETG?

PETG (polyethylene terephthalate glycol) is a tough copolyester thermoplastic material. It is an enhanced version of PET (polyethylene terephthalate) in which the glycol component of the PET monomer is modified with the larger monomer molecule, cyclohexane dimethanol. This modification lowers the material’s crystallinity, slightly reduces its processing temperature, and increases its toughness, compared with the original PET. This corrects the tendency of PET to become cloudy due to crystallization at elevated temperatures.

PETG is used in a wide range of applications because of its toughness, low price, and high degree of formability. It responds well to biaxial orientation—hot stretching in the two axes relative to a sheet handling machine, MD (machine direction), and TD or XD (transverse or cross direction).

Polycarbonate vs. PETG: Applications and Uses

Listed here are the leading market sectors that utilize polycarbonate (extruded/calendered sheet, and molded items) and their applications:

1. Medical Equipment: Cameras, lenses, medical aids
2. Protective Eyewear: Safety goggles and face shields
3. Optical Components: Human vision corrective and instrument lenses, light guides
4. Automotive: Light covers and lenses
5. Media Discs: Blu-ray, DVDs, etc.
6. Domestic and Commercial Paneling: Cupboards, kitchen paneling, handles
7. Display Stands/weatherproofing: Advertising displays, protective covers for advertising, weather shields, barriers in public spaces, and bus stops
8. Agriculture: Greenhouse roofing/windows
9. Lightweight Luggage: Bags and suitcases

Applications for PETG are less diverse than for PC, but are high volume. Examples are:

1. Baby Products: Baby food containers and water bottles
2. Medical: Packaging applications, implants, and prosthetics
3. Signage: Strong color results and high UV stability make PETG a good choice in outdoor display and signage applications
4. Engineering: PETG is finding increasing use in machine component applications, because of its easy processing and high strength/durability

Polycarbonate vs. PETG: Physical Properties

Table 1 below compares the physical properties of polycarbonate and PETG:

Polycarbonate vs. PETG: Recyclability and Sustainability

Polycarbonate (PC) is manufactured from hydrocarbon materials. PC is recyclable and responds well to mechanical recycling processes, such as shredding and re-melt extrusion. However, effective recycling requires rigorous sorting to minimize contamination, as impurities can significantly degrade material performance. PETG is typically marked with a resin identification code ♹ (Type 1 – PET), which can cause confusion in recycling streams because standard PET is also labeled with ♳ (Type 1). In practice, many recycling facilities do not distinguish PETG from PET, leading to contamination issues if mixed. A significant portion of PETG is used in single-use applications, such as product packaging and disposable containers. As a result, much of the PETG waste stream is incinerated, landfilled, or released into the environment, especially where proper waste management infrastructure is lacking.

Polycarbonate vs. PETG: Cost

Polycarbonate (PC) is a specialty, low-volume engineering thermoplastic with a relatively high material cost. Virgin PC resin typically sells for around $2.80 per kg, depending on grade, region, and purity. Where recycling infrastructure exists, high-quality recycled PC can be sourced at approximately $1.60 per kg. PETG is a higher-volume, commodity copolyester used across many applications, including packaging, signage, and particularly 3D printing. In 3D printing markets, PETG filament retails for $20–55 per kg, with price variation based on diameter tolerance, brand, and added properties such as UV resistance or carbon fiber reinforcement. As injection molding or extrusion-grade pellets, PETG pricing is generally lower than that of other materials. Partially recycled, clear PETG granules are available from around $1.10 per kg, while virgin, clear PETG resin typically ranges from $1.60 to $1.80 per kg, depending on supplier and order volume. Color-matched PETG masterbatch granules, used for tinting or opaque applications, can cost up to $4.00 per kg, particularly when customized or compounded with performance additives.

Alternative Materials to Polycarbonate and PETG

Alternative material options for polycarbonate (PC) are highly dependent on the application. Examples of alternative materials are:

1. Acrylic offers some advantages, such as better scratch resistance and lower temperature working, but it is considerably less strong than other materials. Acrylic provides good clarity, but a lower refractive index, making it suitable for windows, but less so for lenses. In this case, urethane materials such as Trivex™ offer advantages.
2. In lower-grade transparent applications, polystyrene (PS) offers an alternative to PC, but it is considerably weaker and highly prone to fracture. However, for applications such as light guides, PS can serve well.
3. In many cases, ABS is a good alternative to PC, where ultimate strength and flexural resilience are less critical.

PETG is an excellent solution to a wide range of packaging and product needs. Alternatives exist in all the sectors where it is employed. For example, in packaging films (generally biaxially oriented), alternatives are: BOPP (polypropylene), BOPE (polyethylene, both HDPE and LDPE), PET, and PVC (polyvinyl chloride). For molded and subsequently blow-molded bottles, alternatives are: PET, HDPE, LDPE, and ABS. For food handling/container applications, alternatives are: HDPE, PP (polypropylene), and ABS.

Summary

This article presented polycarbonate and PETG, explained each of them, and discussed their applications and differences. To learn more about polycarbonate and PETG, contact a Xometry representative.

Xometry provides a wide range of manufacturing capabilities and other value-added services for all of your prototyping and production needs. Visit our website to learn more or to request a free, no-obligation quote.

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1. Trivex™ is a registered trademark of PPG Industries Ohio, Inc.

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